This nonprovisional application claims priority under 35 U.S.C. xc2xa7 119(a) on Patent Application No. 2002-148914 filed in Japan on May 23, 2002, which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to a device for driving optical system for writing or reading information to and from an optical recording medium such as DVD. More particularly, it relates to a supporting mechanism and a driving mechanism for the optical system.
2. Description of the Background Art
A well-known device for driving optical system is introduced in Japanese Patent Application Laid-Open No. 2001-297460. FIG. 17 is a perspective view illustrating a background-art device for driving optical system disclosed therein. The device given in FIG. 17 is a driving device for optical system in which an objective lens 101 is controlled by moving coil system. The objective lens 101 is fixed to a lens holder 102. Provided on the side surfaces of the lens holder 102 are six strip metal plates 103a through 103c, and 103d through 103f. Print coils 104a and 104b are fixed to other side surfaces of the lens holder 102. A base member 105 has a suspension holder 106 for supporting the lens holder 102, and permanent magnets 107a through 107d for controlling the lens holder 102. The strip metal plates 103a through 103c and 103d through 103f are connected to the suspension holder 106 by suspension wires (linear elastic bodies) 108a through 108c and 108d through 108f, respectively, to support the lens holder 102 on the base 105 member. The print coil 104a is interposed between the permanent magnets 107a and 107b, and the print coil 104b is interposed between the permanent magnets 107c and 107d. 
Next, the operations of the background-art device will be discussed. When a current is supplied to focusing coils embedded in the print coils 104a and 104b (not shown) so as to generate electromagnetic forces to act on the coils in the same direction, the lens holder 102 is displaced in the direction Fo of an optical axis (hereinafter alternatively referred to as focusing direction). Further, when a current is supplied to tracking coils embedded in the print coils 104a and 104b (not shown) so as to generate electromagnetic forces to act on the coils in the same direction, the lens holder 102 is displaced in a tracking direction Tk that is a radial direction of an optical recording medium. Still further, when a current is supplied to the focusing coils (not shown) so as to generate electromagnetic forces to act on the coils with the opposite directions, rotation moment about the tracking direction Tk as an axis thereof is applied to the lens holder 102. As a result, the lens holder 102 is rotated in a tilting direction Ti. FIG. 18 is a sectional view illustrating how the lens holder is rotated in the tilting direction Ti. If the electromagnetic forces are generated to act on the focusing coils (not shown) in the opposite directions, the strip metal plates 103a and 103c are displaced and distorted towards the opposite directions by the same amount. As a result, a center of the strip metal plate 103b will be a center O of rotation in the tilting direction Ti, thus rotating the lens holder 102 to an angle xcex8 and displacing the same in the tilting direction Ti. Triaxial drive, namely, drive in the focusing direction Fo, tracking direction Tk, and in the tilting direction Ti, is thereby allowed.
For realizing triaxial drive, the background-art device requires two electric wires for supplying current to the focusing coil in the print coil 104a, two electric wires for supplying current to the focusing coil in the print coil 104b, and two electric wires for supplying current to the tracking coils in the print coils 104a and 104b, respectively. Namely, a total of six electric wires are required. For this reason, the six suspension wires 108a through 108f for supporting the lens holder 102 are also used as electric wires for current supply in the background-art device.
In the background-art device for driving optical system, however, the suspension wires 108a through 108f should contact the strip metal plates 103a through 103f on the side of the lens holder 102. Therefore, the background-art device necessarily requires six strip metal plates, leading to the increase in number of parts. As a result, the problems involving rise in cost of the parts and increase in number of assembly steps have been unavoidable. In the background-art device, further, the suspension wires 108a through 108f and the strip metal plates 103a through 103f should be respectively connected. Therefore, variations of the parts may occur in the assembled condition, resulting in unevenness in performance of the devices.
It is therefore an object of the present invention to provide a device for driving optical system only requiring at least six suspension wires (linear elastic bodies) for supporting a lens holder while allowing triaxial drive, namely, drive in a focusing direction, in a tracking direction, and in a tilting direction.
The device for driving optical system includes an optical system, a holder, a support member, a support system, a focusing drive system, a tracking drive system, and a tilting drive system. The optical system focuses light on an optical recording medium and irradiating the optical recording medium with focused light. The holder holds the optical system. The support member supports the holder. The support system includes at least six linear elastic bodies having the same length. The linear elastic bodies respectively have one ends fixed to the support member and arranged thereon approximately in a circle, and other ends fixed to the holder and arranged thereon approximately in a circle, to support the holder on the support member. The focusing drive system drives the holder in a direction of an optical axis of the optical system. The tracking drive system drives the holder in a radial direction of the optical recording medium. The tilting drive system drives the holder in a direction in which rotation moment generates about an axis. This axis is perpendicular to the direction of the optical axis and to the radial direction of the optical recording medium.
One ends of the at least six linear elastic bodies are fixed to the support member and arranged approximately in a circle thereon, and other ends of the six linear elastic bodies are fixed to the holder and arranged approximately in a circle thereon. The holder is thereby supported on the support member. Therefore, while allowing triaxial drive, cost reduction of parts is realized and the number of assembly steps is reduced. Further, variations of the parts can be reduced in the assembled condition, thus reducing the degree of unevenness in performance of the devices.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.